The copolymers of olefins with vinyl aromatic monomers, in particular styrene, known up to now are of the statistical type or are of the block type, in which, however, the polystyrenic block has an atactic structure. Considering the type of structure of the polystyrenic block, these copolymers do not show properties of practical interest. There is no knowledge up to now of block copolymers of styrene with alpha-olefins, in which the polystyrenic block has sufficiently long stereoregular structure with possibility, therefore, of producing crystallinity of polystyrenic type detectable by means of X-rays.